Storage container, method for molding resin, and method for forming plating film

ABSTRACT

A storage container is provided, which includes carbon dioxide containing a functional material and a container body in which carbon dioxide has been hermetically contained. Accordingly, a method for molding a resin, a method for forming a plating film, and the storage container for carbon dioxide, which are excellent in the mass productively at low cost, are provided without using any special high pressure apparatus for producing a supercritical fluid.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a storage container filled with carbondioxide containing a functional material (modifying material), and amethod for molding a resin and a method for forming a plating film, byusing carbon dioxide containing the functional material.

2. Description of the Related Art

The electroless plating method has been hitherto widely used as a methodfor forming a metal conductive film on a surface of an electronic devicecomprised of a plastic structural member. The electroless platingprocess for the plastic somewhat varies depending on, for example, thematerial of the plastic. However, in general, the respective steps ofresin molding, degreasing of a molded article, etching, neutralizationand wetting, addition of catalysts, activation of catalysts, andelectroless plating are performed in this order.

For example, a chromic acid solution or an alkali metal hydroxidesolution is used as the etching solution in the etching step of theelectroless plating process described above, and results in the factorto increase the cost, because the etching solution as described aboverequires any after treatment such as the neutralization. Further, ahighly toxic etchant is used in the etching step of the electrolessplating process described above. Therefore, a problem arises in relationto the handling in view of the environment. In Europe, the instructionof RoHS (Restriction of the use of certain Hazardous Substances inelectrical and electric equipment) has been established, which restrictsspecified harmful chemical substances contained in electric andelectronic products. Materials and parts supply manufacturers arerequired to guarantee the fact that hexavalent chromium or the like isnot contained in new electric and electronic devices to be introducedinto the European market after Jul. 1, 2006. In view of thecircumstances as described above, the conventional electroless platingprocess for the plastic, which involves the large environmental load, isconfronted with the essential task to make the transfer to anysubstitutive technique.

In order to dissolve the problem involved in the conventional techniquefor forming the electroless plating film for the plastic, for example, anovel plastic electroless plating method, which is based on the use ofthe supercritical fluid, is proposed in “Latest Application Techniquefor Supercritical Fluid” (written by Teruo HORI, NTS Publication, pp.250-255 (2004)). According to the method described in “LatestApplication Technique for Supercritical Fluid”, the metal complex can beinjected into the polymer surface by dissolving the organic metalcomplex in carbon dioxide in the supercritical state (hereinafterreferred to as “supercritical carbon dioxide” as well) to bring intocontact with various types of polymers. Metallic fine particles aredeposited on the polymer surface by performing the reducing treatmentsuch as the chemical reducing treatment or the heating for the polymerinto which the metal complex is injected. Accordingly, the entirepolymer surface can be subjected to the electroless plating. Accordingto this process, it is seen that the electroless plating process for theplastic having the good surface roughness can be achieved, in which itis unnecessary to perform any treatment for the waste liquid.

The present inventors have suggested, for example, in Japanese PatentNo. 3696878, a method for producing a molded article in which afunctional material such as a metal complex is dissolved beforehand insupercritical carbon dioxide, and the functional material is impregnatedinto the surface of the molded article during the injection molding byapplying the principle described in “Latest Application Technique forSupercritical Fluid”. In this method, the functional material isimpregnated into the melted resin by bringing the supercritical carbondioxide, in which the functional material has been dissolved, intocontact with the melted resin. After that, the injection molding isperformed to produce the molded article.

A foam molding process is suggested as an injection molding processindustrially practiced by utilizing the supercritical fluid, forexample, in Japanese Patent Application Laid-open No. 2001-150504. Inthe molding method disclosed in Japanese Patent Application Laid-openNo. 2001-150504, an inert gas such as N₂ or carbon dioxide is used as afoaming agent without using any conventional chemical foaming agent. Theinert gas in the supercritical state is kneaded with a melted resin. Thekneading is performed while mixing a resin material to be plasticizedand melted and a supercritical fluid such as N₂ or CO₂ in a screw whenthe resin material is plasticized and weighed by using the screw.

Various methods have been also hitherto suggested as techniques formodifying the polymer by utilizing the supercritical fluid in order toprovide the highly advanced function such as, for example, theimprovement in the wettability of the surface of the polymer basematerial. For example, Japanese Patent Application Laid-open No.2001-226874 discloses the method for forming the hydrophilic fibersurface by bringing dissolving a supercritical fluid, in which polyalkylglycol has been dissolved, into contact with the fiber. Japanese PatentApplication Laid-open No. 2002-129464 discloses a batch process torealize the highly advanced function of a surface of a polymer basematerial. Specifically, the supercritical fluid, in which the solute asthe functional material has been previously dissolved, is brought intocontact with the polymer base material in a supercritical state, i.e.,at a high pressure to perform the dyeing.

Japanese Patent Application Laid-open No. 2002-313750 also discloses thefollowing method. At first, a mask, in which holes having desired shapesare formed, is provided on a substrate. Then, a supercritical fluid, inwhich a substance (metal complex) to be adhered onto the substrate hasbeen dissolved, is jetted onto the mask to form a pattern of not morethan 100 μm of the adhered substance on the substrate.

Further, for example, a method is also suggested in Japanese PatentApplication Laid-open No. 2005-305945, in which a plating catalyst core(metal complex) is impregnated into a part of surface of a polymer basematerial by using a technique for modifying the surface of the polymerbase material based on the use of a supercritical fluid, and then, aplating film is formed on the polymer base material. In Japanese PatentApplication Laid-open No. 2005-305945, the following method is suggestedas a method for selectively impregnating the metal complex into the partof the surface of the polymer base material. At first, the metal complexis added to a wide area or the entire area of the surface of the polymerbase material. Subsequently, a mold surface, which has a predeterminedconcave/convex pattern, is brought into tight contact with or adhesionto the surface of the polymer base material. Subsequently, thesupercritical fluid is allowed to flow into the space defined by themold (concave portion or recess) and the surface of the polymer basematerial. The metal complex is selectively impregnated into only thesurface area of the polymer base material into which the supercriticalfluid is allowed to flow.

The method, which is disclosed in “Latest Application Technique forSupercritical Fluid” described above, is the batch process. Therefore,this method can be industrially practiced when a large amount of fiber,sheet or the like can be processed in a high pressure vessel. However,in this principle, the polymer surface is softened by the supercriticalcarbon dioxide or the like, and the supercritical fluid and the metalcomplex as the modifying material (functional material) are impregnatedinto the polymer. Therefore, when a large-sized injection moldingarticle or plastic is produced, the method is difficult to beindustrially practiced, because it is difficult to maintain the shape ofthe polymer by softening thereof. Further, the high pressure vessel andthe apparatus for generating the supercritical carbon dioxide are thefactors to increase the cost.

Nitrogen or carbon dioxide in the supercritical state is also broughtinto contact with the resin in the melted state or the solidified statein the techniques disclosed in Japanese Patent No. 3696878 and JapanesePatent Application Laid-open Nos. 2001-150504, 2001-226874, 2002-129464,2002-313750, and 2005-345945 described above. The apparatus forgenerating the supercritical fluid is the factor to increase the cost inthe same manner as in the technique disclosed in “Latest ApplicationTechnique for Supercritical Fluid” described above.

More specifically, in the case of the conventional technique asdescribed above, when carbon dioxide is used as the medium fordissolving the functional material, it is necessary that the pressure ispreviously raised to not less than 7.38 MPa, and the temperature israised to not less than 31° C. to provide the supercritical state.Therefore, the task resides in the long term reliability of the seal ofthe piping and the apparatus for generating the supercritical fluid.Further, it is necessary to provide a step of pressurizing carbondioxide and an expensive high pressure pump and/or a high pressuredissolution tank for dissolving the solute (functional material). Thesematters bring about the factor to increase the cost when the moldedarticle is mass-produced.

SUMMARY OF THE INVENTION

The present invention has been made in order to solve the problems asdescribed above. An object of the present invention is to provide amethod for molding a resin in which a functional material is impregnatedinto the surface and/or the interior of a molded article without usingany special high pressure apparatus for producing the supercriticalfluid as the factor to increase the cost as described above, a methodfor forming a plating film on the surface of the resin, and a storagecontainer for carbon dioxide to be used for the foregoing methods sothat a method for forming a resin, a method for forming a plating film,and a supply source of carbon dioxide, which involve the low cost andwhich are excellent in the mass productivity, are provided.

According to a first aspect of the present invention, there is provideda storage container comprising:

carbon dioxide which contains a functional material; and

a container body in which the carbon dioxide has been hermeticallycontained (the container body is gas-sealed).

The state of carbon dioxide to be charged into the storage container ofthe present invention may be either the supercritical state or a statein which the temperature is lower than and/or the pressure is lower thanthose of the critical point of the supercritical state (31° C., 7.38MFa), i.e., a state in which carbon dioxide gas and liquid carbondioxide coexist (hereinafter referred to as “gas-liquid coexistingstate”, “gas-liquid intermixed state”, or “gas-liquid mixed state” aswell).

As a result of diligent investigations performed by the presentinventors in relation to the method for molding the resin based on theuse of the supercritical carbon dioxide, the following fact has beenrevealed. That is, some functional materials, which are soluble in thesupercritical carbon dioxide or the high pressure (pressurized) carbondioxide gas, are also soluble in the low pressure carbon dioxide in aliquid state. The some functional material can be preserved (stored) insuch a state that the functional material (modifying material) isdissolved in the liquid carbon dioxide which is filled in thetransportable high pressure container (storage container) such as a highpressure bomb.

The present inventors have found out the following fact. That is, evenwhen the resin in the melted state is allowed to be in a reducedpressure atmosphere, and then the carbon dioxide in the liquid state,which does not arrive at the supercritical condition, is introduced orinjected into the melted resin, the liquid can be introduced or injectedinto the melted resin in a high pressure cylinder such as a moldingmachine. Further, the present inventors have found out the followingfact. That is, in this situation, the introduced liquid carbon dioxideinstantaneously undergoes the volume expansion due to the contact withthe high temperature resin in the high pressure cylinder or the like toprovide the supercritical state. Carbon dioxide and the functionalmaterial dissolved therein are easily impregnated into the melted resin.

Therefore, when the resin is molded by using the storage container ofthe present invention, the functional material can be impregnated intothe resin merely by bringing the melted resin into contact with carbondioxide in which the functional material has been dissolved. Therefore,when the resin is molded by using the storage container of the presentinvention, it is unnecessary to separately prepare any special highpressure apparatus for producing the supercritical fluid unlike theconventional technique. Therefore, it is possible to provide the methodfor molding the resin and the method for forming the plating film inwhich the cost is lower and the mass-productivity is excellent. Further,the storage container of the present invention is preferably usable as ainexpensive supply source of the functional material and carbon dioxide.

Any arbitrary functional material may be dissolved in carbon dioxide inthe storage container of the present invention. Specifically, it may beused, for example, various dyes, polyalkyl glycol, fluorine compounds,low molecular weight polymers, and low molecular weight monomers.

In the storage container of the present invention, the functionalmaterial may be a hydrophilic material such as polyalkyl glycol, or ahydrophobic material such as silicone oil and fluorine-based materials.For example, the wettability of the resin surface can be improved byintroducing a polymer or a monomer having an amide group or a hydroxylgroup including, for example, polyalkyl glycol, acrylamide, ands-caprolactam. The water-shedding quality can be added to the resinsurface by using, for example, fluorine-based compounds or silicone oil.

In the storage container of the present invention, the functionalmaterial may be metallic fine particles of the metal complex or theprecursor of metal oxide. When the metallic fine particles are used, themetallic fine particles, which serve as the catalyst core for theelectroless plating, can be impregnated into the surface of the polymerbase material. The conductivity and the thermal conductivity can beadded to the polymer base material by using the metallic fine particlesof, for example, the metal complex or the metal alkoxide to impregnatethe metallic fine particles into the surface of the polymer basematerial.

In the storage container of the present invention, the functionalmaterial may be inorganic fine particles. When the inorganic fineparticles of, for example, SiO₂, Al₂O₃, Cr₂O₃, or TiO₂ are used as thefunctional material, it is possible to suppress the coefficient ofthermal expansion of the polymer base material. When the inorganic fineparticles of, for example, SiO₂ are used as the functional material, itis possible to control the refractive index of the polymer basematerial. When the inorganic substance as described above is used as thefunctional material, it is desirable that the precursor of the rawmaterial is used, or any chemical or physical modification is applied tothe inorganic substance so that the inorganic substance is soluble inthe liquid carbon dioxide.

In the storage container of the present invention, the functionalmaterial may be a surfactant. When the surfactant is used as thefunctional material, the effect is expected to improve the wettabilityof the polymer base material and the prevention of the electrification.

The material, which is usable as the functional material other than thematerials described above, includes, for example, ultravioletstabilizers such as benzophenone and coumarin, aromatic agents, monomersof various polymers such as methyl methacrylate and polymerizationinitiating materials, and chemicals.

In the present invention, the pressure is arbitrary in the storagecontainer for the liquid carbon dioxide. However, in order tosufficiently maintain the solubility of the functional material, thestorage container may be used at least not less than 3 MPa, and moredesirably not less than 5 MPa. In view of the safety and the qualitycontrol of the storage container, the pressure of carbon dioxide in thestorage container may be not more than 15 MPa, and more desirably notmore than 7.38 MPa at which carbon dioxide is in the supercriticalstate.

According to the laws and ordinances in Japan, it is specified that thefilling constant C of the storage container, which is represented byC=V/G (G: mass of liquefied gas, V: container internal volume of thebomb), is not more than 1.34. FIG. 6 shows the relationship between thetemperature and the pressure in the storage container when carbondioxide is filled or charged in accordance with the provision of thelaws and ordinances. When the temperature is 14° C., then a state isgiven, in which the liquid is 90% and the gas coexists in the upperlayer in the storage container, and the pressure is 4.9 MPa. When thetemperature is 22° C., then the entire content of the container is theliquid, and the pressure is 5.9 MPa. When the temperature exceeds thecritical temperature (31° C.), then the entire content of the containeris the gas or the supercritical state. It is prescribed that the safetyplate bursts when he temperature is further raised to arrive at a statehaving the pressure of 15.7 MP.

The method is arbitrary to collect and supply carbon dioxide in whichthe functional material has been dissolved, from the storage containerfilled with carbon dioxide according to the present invention.Specifically, for example, when carbon dioxide is in the gas-liquidcoexisting state (state which does not arrive at the critical point ofthe supercritical state), it is possible to collect and use only theliquid carbon dioxide, in which the functional material has beendissolved, with a siphon tube. The reason thereof will be explainedbelow.

FIGS. 7 and B show results of the measurement of the pressure change inthe bomb when carbon dioxide is taken out continuously at a constantflow rate by using the conventional liquid carbon dioxide bomb filledwith 30 kg. FIG. 7 shows the characteristic obtained when the bomb,which is not provided with the siphon tube, is used. FIG. 8 shows thecharacteristic obtained when the bomb, which is provided with the siphontube, is used. The measurement temperature condition was about 14° C. asa winter environment. The pressure, which is obtained when the bomb isfully filled, is about 5 MPa at this temperature. As a result diligentinvestigations performed by the present inventors, in the case of thebomb which is not provided with the siphon tube, as shown in FIG. 7, thepressure in the container is suddenly lowered in accordance with theprogress of the use of carbon dioxide (elapsed time depicted on thehorizontal axis in FIG. 7), and it is impossible to maintain anyconstant pressure in the container. On the other hand, in the case ofthe bomb which is provided with the siphon tube, it is possible toselectively collect the liquid phase existing in the lower layer in thebomb. Therefore, the following fact has been revealed. That is, when theflow rate is sufficiently small (for example, 10 [1/min]), as shown inFIG. 8, the pressure in the container is not suddenly lowered inaccordance with the progress of the use of carbon dioxide (elapsed timedepicted on the horizontal axis in FIG. 8), and it is possible to stablymaintain the pressure.

In the case of the storage container of the present invention, it isdesirable that the temperature of the storage container is not more than31° C. as the critical point of the supercritical state of carbondioxide. More favorably, it is desirable that the temperature is notmore than 22° C. at which the interior of the storage container, whichsatisfies the provision of the filling constant C of the bomb, is in thegas-liquid coexisting state. In this situation, the liquid carbondioxide, in which the functional material has been dissolved, can besupplied from the storage container at a stable pressure of not morethan about 5.9 MPa. In this case, when the amount of use of the liquidcarbon dioxide is increased, then the liquid level of the liquid surfaceis lowered, and the amount of the gas is increased correspondingthereto. Therefore, when the temperature of the storage container is notmore than 22° C., the carbon dioxide, in which the functional materialhas been dissolved, can be always supplied stably at a constant pressurein the liquid state, which is preferred.

As shown in FIG. 8, when the flow rate of the liquid carbon dioxide issmaller, the liquid carbon dioxide can be supplied at a stable pressure.Therefore, when it is intended to increase the flow rate of the liquidcarbon dioxide to be supplied, the following method is favorablyadopted. That is, the storage containers are connected in parallel, andthe liquid carbon dioxide is allowed to outflow simultaneously from therespective storage containers.

As for the method for collecting and supplying carbon dioxide in whichthe functional material has been dissolved, from the storage containerof the present invention, it is also appropriate to adopt a method inwhich the temperature and the pressure of the storage container areincreased, other than the method in which only the liquid phase is takenout from carbon dioxide in the gas-liquid intermixed state as describedabove. However, in this method, for example, when the carbon dioxide,which is contained in the storage container, is the gas exceeding thecritical temperature or in the supercritical state, it is inevitablethat the pressure is lowered as the carbon dioxide is consumed. As aresult, when the carbon dioxide is consumed, the solubility of thefunctional material is changed in the high pressure container.Therefore, when this method is used, it is preferable to adopt thefollowing method as a method for stabilizing the solubility of thefunctional material and the supply pressure of carbon dioxide to besupplied, for example, to the molding machine.

For example, the following procedure is preferred. At first, thetemperature is set beforehand so that the internal pressure of thestorage container is about 10 to 15 MPa. Then, the internal pressure ofthe storage container, which is located in the primary or upstream side,is once reduced by using, for example, a pressure-reducing valve.Subsequently, carbon dioxide is supplied to the apparatus such as themolding machine in a state in which the temperature and the pressure ofcarbon dioxide are constant on the secondary or downstream side of thepressure-reducing valve or the like. In the case of this method, it isdesirable that the charge amount of the functional material into thestorage container is adjusted so that the solubility of the functionalmaterial contained in the storage container is not more than thesaturation solubility at the pressure and the temperature of carbondioxide on the secondary side subjected to the pressure reduction as thesupply pressure to the apparatus. The pressure in the storage containerduring the initial filling, is sufficiently higher than the pressure onthe secondary side. Therefore, the functional material, which has beendissolved in the unsaturated state, approaches the saturated state inaccordance with the consumption of the carbon dioxide and the functionalmaterial in the storage container. As a result, the deposition of thefunctional material is suppressed as well.

The storage container of the present invention may further comprise astirring apparatus in order to stabilize the solubility of thefunctional material in the liquid carbon dioxide. An apparatus may beused as the stirring apparatus, which includes, for example, a stirringbar which is provided in the container body, and a magnetic stirrerwhich is provided outside the container body in order to drive thestirring bar. In this arrangement, when the container body of thestorage container is formed of a nonmagnetic material, the stirring bar,which is contained in the container body, can be rotated by means of theexternal magnetic stirrer. Accordingly, it is possible to stabilize thesolubility of the functional material contained in the liquid carbondioxide. The nonmagnetic material, which is usable for the containerbody of the storage container, includes, for example, aluminum,stainless steel, inconel, hastelloy, and titanium. An ultrasonicgenerator may be provided as the stirring apparatus at the outside ofthe container body. In this arrangement, it is possible to stabilize thesolubility of the functional material contained in the container body byapplying the ultrasonic wave to the liquid carbon dioxide contained inthe container body.

In the storage container of the present invention, an organic solventsuch as alcohol and acetone may be mixed and used as an auxiliary agentin the container body in order to stabilize or improve the solubility ofthe functional material with respect to carbon dioxide.

According to a second aspect of the present invention, there is provideda method for molding a resin, comprising:

preparing liquid carbon dioxide containing a functional material; and

impregnating the functional material into the resin by bringing theliquid carbon dioxide into contact with the resin having a temperaturehigher than that of the liquid carbon dioxide.

In the molding method of the present invention, a state of the resin maybe controlled so that the liquid carbon dioxide is changed into one ofcarbon dioxide in a supercritical state and high pressure carbon dioxidegas when the liquid carbon dioxide is brought into contact with theresin.

The present inventors have found out, by a verifying experiment, thefact that the functional material is impregnated into the resin evenwhen the liquid carbon dioxide, which has been dissolved with thefunctional material and which is in the state of low temperature and/orlow pressure of not more than the critical point of the supercriticalstate, is brought into contact with the resin having a temperaturehigher than that of the liquid carbon dioxide. This phenomenon isconsidered as follows. That is, even when the liquid carbon dioxide isin the state of low temperature and/or low pressure of not more than thecritical point of the supercritical state, the liquid carbon dioxideinstantaneously has a high temperature by bringing into contact with themelted resin having the high temperature. When the temperature is raisedto be high while maintaining a constant volume, the high pressure stateor the supercritical state is given. Then, the liquid carbon dioxide isdiffused at a high velocity into the resin. Alternatively, the followingconsideration may be made. That is, as the pressure is raised, forexample, by the holding pressure for the thermoplastic melted resin, thepressure and the diffusibility of carbon dioxide are improved in thesame manner as described above. Accordingly, the functional material,which has been dissolved in the liquid carbon dioxide, can beimpregnated into the resin in the heated, melted, or semi-melted state.

In the molding method of the present invention, any arbitrary method maybe available to impregnate, into the resin, the carbon dioxide in whichthe functional material has been dissolved. For example, the carbonoxide may be impregnated into a vent-portion of a vent-type screw, i.e.,into a physical pressure-reducing mechanism portion in a plasticizingcylinder of an extrusion molding machine or an injection moldingmachine. In this case, the carbon dioxide and the functional materialcan be impregnated into the whole or a part of the melted resin whileplasticizing the resin.

In the molding method of the present invention, the method for moldingthe resin may be a method for molding a thermoplastic resin based on theuse of an injection molding machine provided with a plasticizingcylinder for injecting a melted resin into a mold; the method formolding the thermoplastic resin comprising: introducing the liquidcarbon dioxide containing the functional material into a flow frontportion of the plasticizing cylinder to bring the liquid carbon dioxideinto contact with the melted resin in the plasticizing cylinder so thatthe functional material is impregnated into the melted resin; andinjecting the melted resin in the plasticizing cylinder into the mold tofill the mold therewith.

In the molding method based on the injection molding of the presentinvention, the method is arbitrary to impregnate the functional materialinto the flow front portion. However, for example, the following processmay be adopted. At first, when the injection molding is performed, thescrew is moved backwardly in ordinary cases in accordance with theincrease in the internal pressure of the resin disposed in front of thescrew by performing the plasticization and the weighing while rotatingthe screw. In the molding method of the present invention, the screw ismoved backwardly without rotating the screw after the weighing to reducethe pressure in the melted resin disposed in front of the screw (on theside of the mold). Subsequently, the liquid carbon dioxide and thefunctional material, which are at the pressure higher than the internalpressure of the melted resin, are impregnated into the forward endportion (flow front portion) in the melted resin in the state of reducedpressure. The back pressure at the back of the screw is raised, and thusthe screw is moved frontwardly again. In accordance with the method asdescribed above, the carbon dioxide, which is at the high temperatureand the high pressure, for example, in the supercritical state, can bediffused into the flow front portion of the resin together with thefunctional material dissolved in the carbon dioxide. When the injectionmolding is performed (the cavity defined in the mold is filled) afterimpregnating the functional material into the flow front portion, thefunctional material, which is disposed at the flow front portion, isdiffused to the surface of the molded article due to the fountain effectof the filling resin (skin layer is formed). As a result, it is possibleto mold the injection molding article in which the functional materialis dispersed in the skin layer (is impregnated into the surface).

In the molding method of the present invention, the method for moldingthe resin may be a method for molding a thermoplastic resin based on theuse of an extrusion molding machine: the method for molding thethermoplastic resin comprising: bringing the liquid carbon dioxidecontaining the functional material into contact with the thermoplasticresin which is in a melted state or a softened state in the extrusionmolding machine so that the functional material is impregnated into thethermoplastic resin; and performing extrusion molding for thethermoplastic resin into which the functional material has beenimpregnated.

In the molding method based on the extrusion molding of the presentinvention, for example, the liquid carbon dioxide, in which thefunctional material has been dissolved, is firstly introduced andimpregnated from the storage container (for example, the bomb) filledwith the carbon dioxide dissolved with the functional material into thethermoplastic resin in the melted or softened state in the extrusionmolding machine. In this method, the resin, into which the functionalmaterial has been impregnated, is subjected to the extrusion molding.The method for impregnating the liquid carbon dioxide dissolved with thefunctional material into the thermoplastic resin in the melted orsoftened state includes, for example, the following method. That is, theinternal pressure of the melted resin is reduced at least at a part ofthe extrusion die or the extrusion screw provided with thepressure-reducing mechanism, and the liquid carbon dioxide and thefunctional material are continuously or intermittently introduced intothe reduced pressure portion of the resin. Accordingly, the liquidcarbon dioxide, in which the functional material has been dissolved, isimpregnated into the melted resin. When the molding method as describedabove is used, it is possible to modify the surface or the interior ofthe molded article with the functional material.

In the molding method of the present invention, the preparation of theliquid carbon dioxide containing the functional material may includepreparing a storage container which is filled with the liquid carbondioxide containing the functional material. In the molding method of thepresent invention, when the storage container such as the bomb filledwith the liquid carbon dioxide dissolved with the functional material,is used as the supply source for the liquid carbon dioxide in which thefunctional material has been dissolved, the liquid carbon dioxide, inwhich the solubility of the functional material is stabilized, can besupplied more easily.

The type of the resin capable of being used in the molding method of thepresent invention is arbitrary. It is possible to use thermoplasticresins, thermosetting resins, and photo-curable resins. Those usable asthe thermoplastic resin include, for example, synthetic fiber such asthose based on polyester, polypropylene, polymethyl methacrylate,polycarbonate, amorphous polyolefin, polyetherimide, polyethyleneterephthalate, liquid crystal polymer, ABS resin, polyamideimide,biodegradable plastic such as polylactic acid, nylon resin, andcomposite materials thereof. It is also possible to use resin materialskneaded, for example, with various inorganic fillers including, forexample, glass fiber, carbon fiber, and nanocarbon. Those usable as thethermosetting resin include, for example, polyimide, silicone resin, andurethane resin. Those usable as the photo-curable resin include, forexample, acrylic resin and epoxy resin. The materials as described abovecan be appropriately selected depending on the way of use.

According to a third aspect of the present invention, there is provideda method for forming a plating film, comprising:

molding a molded article including metallic fine particles impregnatedinto a surface of the molded article by using the method for forming theresin according to the second aspect of the present invention; and

forming the plating film by an electroless plating method on the surfaceof the molded article into which the metallic fine particles have beenimpregnated.

In the molding method of the present invention described above, when themetallic fine particles are used as the functional material, themetallic fine particles can be dispersed in the surface of the moldedarticle (impregnate the metallic fine particles into the surface of themolded article). The metal film can be formed on the surface of themolded article by means of the electroless plating method by using themetallic fine particles as the catalyst core. When the plating method asdescribed above is used, the satisfactory electroless plating film canbe also formed on any polymer base material (resin material) on whichthe surface is hardly roughened by the etching in the case of anyconventional method and on which it has been difficult to form anyelectroless plating film having highly tight contact or adhesionperformance.

According to the storage container of the present invention, it ispossible to supply carbon dioxide in which the functional material hasbeen dissolved with the inexpensive apparatus without using any specialhigh pressure apparatus.

According to the molding method of the present invention, the functionalmaterial can be impregnated into the resin by using the liquid carbondioxide at the low pressure and/or the low temperature of not more thanthe critical point of the supercritical state. Therefore, the moldedarticle, in which the surface and/or the interior is modified with thefunctional material, can be produced without using any special highpressure apparatus to allow carbon dioxide to be in the high pressurestate or the supercritical state. Therefore, the molded article, inwhich the surface and/or the interior is modified with the functionalmaterial, can be easily produced at low cost.

According to the method for forming the plating film of the presentinvention, the metallic fine particles can be dispersed into the surfaceof the molded article at the stage of molding of the molded article. Themetal film can be formed on the surface of the molded article by theelectroless plating method by using the metallic fine particles as thecatalyst core. Therefore, the plating film can be easily formed on thesurface of the molded article without using any solvent which involvesthe large environmental load. According to the method for forming theplating film of the present invention, the satisfactory electrolessplating film can be also formed on any polymer base material (resinmaterial) on which the surface is hardly roughened by the etching in thecase of any conventional method and on which it has been difficult toform any electroless plating film having highly tight contact oradhesion performance.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic arrangement illustrating a molding apparatusused in first to third embodiments.

FIG. 2 shows magnified mold portions of the molding apparatus shown inFIG. 1, which illustrates the initial step of filling the cavity withthe resin.

FIG. 3 shows magnified mold portions of the molding apparatus shown inFIG. 1, which illustrates a state in which the cavity is completelyfilled with the resin.

FIG. 4 shows a schematic arrangement illustrating a molding apparatusused in fourth and fifth embodiments.

FIG. 5 shows the pressure dependence of the solubility of the functionalmaterial used in the embodiments.

FIG. 6 shows the relationship between the temperature and the pressureof the carbon dioxide bomb.

FIG. 7 shows the characteristic of the change of the container internalpressure with respect to the consumption in the carbon dioxide bomb whenany siphon tube is not used.

FIG. 8 shows the characteristic of the change of the container internalpressure with respect to the consumption in the carbon dioxide bomb whenthe siphon tube is used.

FIG. 9 shows a flow chart for explaining the method for molding theresin and the method for forming a plating film on the molded article inthe first embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

An explanation will be specifically made below with reference to thedrawings about embodiments of the storage container, the method formolding the resin, and the method for forming the plating film accordingto the present invention. However, the present invention is not limitedthereto.

First Embodiment

In a first embodiment, an explanation will be made about a method formolding a resin and a method for forming a plating film using aninjection molding machine, and a storage container for supplying, to theinjection molding machine, liquid carbon dioxide in which a functionalmaterial has dissolved.

The type of the resin capable of being used in the molding method ofthis embodiment is arbitrary. It is possible to use, for example,thermoplastic resins including, for example, synthetic fiber such asthose based on polyester, polypropylene, polymethyl methacrylate,polycarbonate, amorphous polyolefin, polyetherimide, polyethyleneterephthalate, liquid crystal polymer, ABS resin, polyamideimide,polylactic acid, nylon resin, and composite materials thereof. It isalso possible to use resin materials kneaded, for example, with variousinorganic fillers including, for example, glass fiber, carbon fiber, andnanocarbon. The materials as described above can be appropriatelyselected depending on the way of use. In this embodiment, polycarbonatehaving a glass transition temperature of 145° C. was used.

In this embodiment, hexafluoroacetylacetonato palladium (II) as themetal complex was used as the functional material to be dissolved in theliquid carbon dioxide. The type of the functional material is arbitrary.It is possible to use, for example, dye or dyestuff, polyalkyl glycol,metallic fine particles of metal complex or the like, and fluorinecompound. The selection of the functional material can be appropriatelydetermined, for example, depending on the way of use. FIG. 5 shows thepressure dependence of the solubility of the metal complex(hexafluoroacetylacetonato palladium (II)) used in this embodiment withrespect to the liquid carbon dioxide (20° C.). Carbon dioxide is in thesuperaritical state under the condition in which the temperature is 31°C. and the pressure is not less than 7.38 MPa. FIG. 5 also shows thepressure dependence of the solubility with respect to carbon dioxide at40° C. (gas state).

The amount of dissolution of the metal complex with respect to carbondioxide was determined by the extraction method. Specifically, at first,the metal complex is charged or put into a pressure vessel so that thesupersaturated state is given. The pressure is raised to a desiredconstant pressure to dissolve the metal complex in carbon dioxide. Afterthat, the internal pressure of the pressure vessel is constantlyretained by a back pressure valve. In this state, a predetermined amountof carbon dioxide is allowed to flow and discharge at a constant flowrate into an alcohol solvent contained in an extraction vessel disposedoutside the pressure vessel by using a syringe pump. The mass of themetal complex, which is extracted into the alcohol solvent, is regardedas the dissolution amount, and the amount of carbon dioxide, which isallowed to flow, is regarded as the solvent amount to calculate thesolubility of the metal complex.

As clarified from FIG. 5, it has been revealed that the metal complexused in this embodiment exhibits the solubility to some extent even inthe gas state at 40° C. and not more than 7 MPa. According to FIG. 5, itis appreciated that the metal complex used in this embodiment has thesatisfactory solubility with respect to the liquid carbon dioxide at 20°C. as well. As described above, it is desirable that the material, whichalso exhibits the solubility to some extent with respect to the lowpressure carbon dioxide of not more than the critical point(supercritical state), is used as the functional material to be used inthe present invention.

[Molding Apparatus]

FIG. 1 shows a schematic arrangement of a molding apparatus used in thisembodiment. As shown in FIG. 1, the molding apparatus used in thisembodiment principally includes an injection molding machine 100 and acarbon dioxide supply unit 101.

As shown in FIG. 1, the injection molding machine 100 principallyincludes a plasticizing cylinder 40 which injects the melted resin, anda mold 26. The mold 26 is composed of a movable mold 19 and a fixed mold18. As shown in FIG. 1, the fixed mold 18 knocks to the movable mold 19in the mold 26 to define a cavity 20 at the interface between the fixedmold 18 and the movable mold 19. The injection molding machine 100 ofthis embodiment is interconnected to an unillustrated electric togglemold-claming mechanism. The movable mold 19 is moved in the horizontaldirection as viewed in the drawing, and thus the mold 26 isopened/closed. As shown in FIG. 1, an introducing port 8 for liquidcarbon dioxide is provided at a side portion of a flow front portion 11in the plasticizing cylinder 40. The other structure of the injectionmolding machine 100 is the same as the structure of any conventionalinjection molding machine.

As shown in FIG. 1, the carbon dioxide supply unit 101 principallyincludes three storage containers 10, a filter 34, a pressure-reducingvalve 60, a first air operate valve 61, a second air operate valve 62,three pressure gauges 23 to 25, and a piping 7 which connects theconstitutive components as described above. As shown in FIG. 1, theoutput side (secondary side) of the second air operate valve 62 isconnected via the piping 7 to the introducing port 8 of the injectionmolding machine 100.

In the present invention, in order to maintain carbon dioxide in theliquid state, it is desirable that the temperature is controlled so thatthe piping and the valves, through which the liquid carbon dioxide isallowed to flow, have the low temperature. In this embodiment, theentire piping 7, through which carbon dioxide is allowed to flow, wasthe double piping (not shown). Carbon dioxide was allowed to flowthrough only the piping disposed on the inner side. Cooling water at 20°C. was allowed to flow by using an unillustrated chiller through thepiping disposed on the outer side of the double piping. In this way, inthis embodiment, carbon dioxide, which is disposed in the piping and thevalves, was always cooled.

In this embodiment, the surrounding of the valve 62 was covered with anunillustrated cooling manifold to cool the manifold and the valve 62 inorder to suppress the increase in the temperature of the second airoperate valve 62 disposed adjacently to the plasticizing cylinder 40having the high temperature. Further, in this embodiment, the piping 12,which is disposed between the first air operate valve 61 and the secondair operate valve 62, could be instantaneously heated from the outsideby means of an unillustrated infrared lamp.

As shown in FIG. 1, the storage container 10 principally includes acontainer body 1 which is formed of aluminum (nonmagnetic material) andis gas-sealed, liquid carbon dioxide 2 with which the interior of thecontainer body 1 is filled (hermetically contained) and in which thefunctional material has been dissolved, a siphon tube 3 which isprovided to take out the liquid carbon dioxide 2 from the storagecontainer 10, a stirring bar 4 which is provided to retain a constantsolubility of the functional material in the liquid carbon dioxide 2,and a magnetic stirrer 5 which is provided to drive and rotate thestirring bar 4. In this embodiment, the carbon dioxide, with which theinterior of the container body 1 is filled, is stored in the gas-liquidmixed state.

In the molding apparatus of this embodiment, as shown in FIG. 1, theoutflow ports for carbon dioxide of the respective storage containers10, each of which is communicated with the interior of the containerbody 1 via the siphon tube 3, are connected to the piping 7 in parallel.In this embodiment, the outflow port for carbon dioxide of each of thestorage containers 10 was in the normally open state.

The storage container 10 of this embodiment is provided with the siphontube 3 to take out only the liquid phase from the interior of thecontainer body 1 in which carbon dioxide is in the gas-liquid mixedstate. Therefore, as described above, the liquid carbon dioxide 2, inwhich the pressure and the solubility are stable, can be supplied to theinjection molding machine 100. In this embodiment, the container body 1is formed of aluminum as the nonmagnetic material. Therefore, thestirring bar 4, which is enclosed in the container body 1, can be drivenand rotated by the magnetic stirrer 5. In this embodiment, the stirringbar 4 was always rotated at 250 rpm to agitate the liquid carbon dioxide2 so that the temperature in the liquid carbon dioxide 2 and thesolubility of the functional material are uniformized.

In this embodiment, the pressure of carbon dioxide contained in thecontainer body 1 is arbitrary. However, in order to maintain thesolubility of the functional material, it is preferable to make the useat least not less than 3 MPa and more desirably not less than 5 MPa. Inview of the safety of the container body 1 and the quality control, thepressure is desirably not more than 15 MPa and more desirably not morethan 7.38 MPa (critical point).

In this embodiment, in order to stabilize the solubility of thefunctional material with respect to carbon dioxide contained in thecontainer body 1, it is desirable that the temperature of the containerbody 1 is controlled. Specifically, it is desirable to make the controlto provide the temperature condition under which carbon dioxidecontained in the container body 1 is in the state of not more than thecritical point, i.e., in the gas-liquid mixed state. In this embodiment,as shown in FIG. 1, the three storage containers 10 were covered with anadiabatic wall 6. The air conditioning was performed so that thetemperature in the adiabatic wall 6 is constant to be 21±1° C.Accordingly, the temperature in the container body 1 regularly filledwith the liquid carbon dioxide 2 was stabilized to make it possible tocontinuously and stably supply the liquid carbon dioxide 2 having apressure in a range of 5.5 to 6 MPa.

In this embodiment, it is desirable that the amount of dissolution(solubility) of the functional material previously dissolved in theliquid carbon dioxide 2 in the container body 1 is not more than thesaturation solubility at the supply pressure of the liquid carbondioxide during the use, in order to maintain the constant solubilitywith respect to the liquid carbon dioxide to be supplied to theinjection molding machine 100. This feature will be explained morespecifically below. For example, as shown in FIG. 5, when the liquidcarbon dioxide having a pressure in a range of 5.5 to 6 MPa is suppliedto the injection molding machine 100, then the solubility of the metalcomplex used in this embodiment with respect to the liquid carbondioxide was about 750 mg/L under the condition of 20° C. and 6 MPa, andthe solubility was about 300 mg/L under the condition of 20° C. and 5.5MPa. That is, in order to stably supply the liquid carbon dioxide underthe condition of 20° C. and 6 MPa, it is appropriate that thedissolution amount (charge amount) of the functional material previouslydissolved in the liquid carbon dioxide 2 in the container body 1 isadjusted so that the solubility is not more than 750 mg/L. In order tostably supply the liquid carbon dioxide under the condition of 20° C.and 5.5 MPa, it is appropriate that the dissolution amount of thefunctional material previously dissolved in the liquid carbon dioxide 2in the container body 1 is adjusted so that the solubility is not morethan 300 mg/L. When the charge amount of the functional material in thecontainer body 1 is adjusted as described above, it is possible tosuppress the fluctuation of the supply amount of the functional materialwhich would be otherwise caused by the slight change of the temperatureand the pressure. Further, it is possible to suppress the excessiveconsumption of the functional material. Accordingly, it is possible tomaintain the constant solubility with respect to the liquid carbondioxide to be supplied to the injection molding machine 100.

In this embodiment, the operating pressure (supply pressure) of carbondioxide to be introduced into the injection molding machine 100 was 5.5MPa as described later on. Therefore, in this embodiment, 200 mg of themetal complex per 1 L of the liquid carbon dioxide was dissolved andused. The container, in which 7 kg of the amount can be maximallycharged per one container, was used for the container body 1. Theregular filling amount was 10 liters. Therefore, the metal complex of10×0.2=2 g was charged per one container body. In this embodiment, themetal complex was previously charged into the container, and then thecontainer was filled with the liquid carbon dioxide. Thus, the metalcomplex was dissolved in the liquid carbon dioxide (step S1 in FIG. 9).

[Method for Molding Resin]

Next, an explanation will be made with reference to FIGS. 1 to 3 and 9about a method for molding the resin in this embodiment.

The liquid carbon dioxide 2, in which the metal complex was dissolved,was introduced into the injection molding machine 100 as follows. Atfirst, the liquid carbon dioxide was allowed to outflow from the threestorage containers 10 so that the indication of the pressure gauge 25shown in FIG. 1 was within a range of 5.5 to 6 MPa. The pressure wasadjusted to 5.5 MPa by means of the pressure-reducing valve 60.Subsequently, the first air operate valve 61 was opened. The liquidcarbon dioxide, in which the metal complex was dissolved, was introducedinto the piping 12 between the first air operate valve 61 and the secondair operate valve 62 to raise the indication of the pressure gauge 24.In this embodiment, when the liquid carbon dioxide, in which the metalcomplex has been dissolved, is introduced into the plasticizing cylinder40 of the injection molding machine 100, then the second air operatevalve 62 is opened in the state in which the first air operate valve 61is closed, and the liquid carbon dioxide is introduced into the meltedresin in the pressure-reduced state as described later on so that thecarbon dioxide and the metal complex are impregnated into the meltedresin. That is, in this embodiment, the amount of introduction of carbondioxide was controlled in accordance with the internal volume of thepiping 12.

Subsequently, the screw 41 was rotated as in the conventional manner,and pellets 15 of the supplied resin were plasticized and melted. Then,the screw 41 was moved backwardly while weighing the melted resin at theportion 22 in front of the screw. The movement of the screw 41 wasstopped at a predetermined weighing position. Subsequently, the screw 41was further moved backwardly to reduce the internal pressure of theweighed melted resin. In this case, the pressure was lowered so that theresin pressure, which was measured with the internal pressure monitor 16of the resin, was not more than 1 MPa.

Subsequently, the second air operate valve 62 was opened. The liquidcarbon dioxide, with which the piping 12 was filled and in which themetal complex was dissolved, was introduced from the introducing port 8into the flow front portion 11 of the plasticizing cylinder 40 to bringinto contact with the melt resin. In this step, the liquid carbondioxide and the metal complex were impregnated into the melted resin(step S2 in FIG. 9). The indication of the pressure gauge 24 was loweredfrom 6 MPa to 3 MPa when the liquid carbon dioxide was introduced.Subsequently, the second air operate valve 62 was closed. After that,the screw 41 was moved frontwardly by means of the back pressure forceto return the screw 41 to the filling start position. Accordingly, thecarbon dioxide and the metal complex were diffused into the melted resinat the flow front portion 11. Then, the air piston 21 was driven to openthe shutoff valve 17. The melted resin was injected into the cavity 20of the mold 26 defined by the fixed mold 18 and the movable mold 19 tofill the cavity 20 therewith (step S3 in FIG. 9).

FIGS. 2 and 3 schematically show the filling situations of the meltedresin in the mold 26 during the injection. FIG. 2 schematically showsthe initial filling situation. In this situation, the metal complex andthe carbon dioxide, which are impregnated into the flow front portion11, are diffused in the cavity 20 while reducing the pressure. In thissituation, the melted resin 27 of the flow front portion 11 is filledwhile bringing into contact with the mold surface due to the fountaineffect during the filling to form the skin layer.

Upon the completion of the filling, as shown in FIG. 3, the layer (skinlayer) 27, into which the metal complex is impregnated, is formed in thevicinity of the surface of the molded article. The layer, into which themetal complex is hardly impregnated, is formed at the core layer 28 ofthe molded article. Therefore, in the case of the molded articleproduced in this embodiment, it is possible to reduce the amount of useof the metal complex, because the metal complex, which is impregnatedinto the inside, does not contribute to the surface function. Further,the foaming, which would be otherwise caused by the gasification ofcarbon dioxide, can be suppressed by increasing the holding pressure ofthe melted resin after performing the primary filling as describedabove. In the molding method of this embodiment, carbon dioxide isimpregnated into only the flow front portion 11 in the plasticizingcylinder 40. Therefore, the absolute amount of carbon dioxide is smallwith respect to the entire filling resin. Therefore, the surfacecharacteristic of the molded article is hardly deteriorated, even whenthe counter pressure is not applied into the mold cavity 20.

In the molded article manufactured by the molding method as describedabove, the palladium metal complex was thermally decomposed, and thefine particles, which were reduced to the metal element of palladium,were dispersed (impregnated) in the vicinity of the surface. The surfaceof the molded article also included portions in which the metal complexwas dispersed without being reduced.

[Method for Forming Plating Film]

Next, a plating film was formed on the surface of the molded articlemanufactured by the molding method as described above (step S4 in FIG.9). Specifically, the plating film was formed as follows.

The molded article manufactured in this embodiment was subjected to thealkali washing and the annealing, and then the molded article wasimmersed in an Ni-P electroless plating solution (Nicoron DK produced byOkuno Chemical Industries Co., Ltd.) to form a nickel plating filmhaving a thickness of 1 μm on the surface of the molded article. As aresult, the nickel film (hereinafter referred to as “first plating film”as well), which had no blister, was successfully formed over the entiresurface of the molded article. After that, a nickel film having a filmthickness of 20 μm was formed on the first plating film by means of theelectroplating method by using, as the electrode, the first plating filmformed by the electroless plating method. The plating film (nickel film)was formed on the surface of the molded article manufactured in thisembodiment in accordance with the method described above. Thecross-hatch peel test was performed for the formed plating film. As aresult, any exfoliation of the plating film was not observed. It wasrevealed that the satisfactory plating film was formed.

Second Embodiment

In this embodiment, the injection molding of the resin was performed byusing the same apparatus as the injection molding apparatus used in thefirst embodiment. In this embodiment, in the same manner as in the firstembodiment, the first air operate value 61 was opened, and the liquidcarbon dioxide, in which the metal complex was dissolved, was introducedinto the piping 12 between the first air operate value 61 and the secondair operate value 62. Accordingly, the pressure at the pressure gauge 24was raised to 5.5 MPa which was the same as the primary pressure.

Subsequently, the infrared lamp was radiated from the outside of thepiping 12 immediately after introducing, into the piping 12, the liquidcarbon dioxide in which the metal complex was dissolved so that thetemperatures of the piping 12 and the carbon dioxide contained thereinwere quickly raised. In this situation, the pressure at the pressuregauge 24 was raised to 14 MPa. As a result, it was confirmed that theliquid carbon dioxide, which was introduced into the piping 12, was inthe supercritical state, and the density was highly concentrated.Subsequently, in the same manner as in the first embodiment, the secondair operate value 62 was opened in the state in which the first airoperate value 61 was closed. The supercritical carbon dioxide and themetal complex were introduced into the plasticizing cylinder 40, andthey were impregnated into the melted resin in the reduced pressurestate. The injection molding was performed in accordance with the samemethod as that of the first embodiment except for the step describedabove. As a result, a molded article, in which the metallic fineparticles were impregnated into the surface thereof, was stably obtainedin the same manner as in the first embodiment.

In this embodiment, the pressure of the liquid carbon dioxide can beincreased in accordance with the inexpensive method before the liquidcarbon dioxide is introduced into the plasticizing cylinder 40. Forexample, it is possible to increase the amounts of introduction of thecarbon dioxide and the functional material into the resin by providingthe supercritical state. Accordingly, the modification efficiency isimproved for the resin.

In this embodiment, a plating film was formed on the surface of themolded article in the same manner as in the first embodiment. As aresult, the metal film, which had the satisfactory tight contact oradhesion, was successfully obtained in the same manner as in the firstembodiment.

Third Embodiment

In the third embodiment, the injection molding of the resin wasperformed by using the same apparatus as the injection molding apparatusused in the first embodiment. However, in this embodiment, the airconditioning was performed so that the temperature in the adiabatic wall6 is constant to be 40±1° C. Accordingly, the pressure in the containerbody 1, which was obtained when the container body 1 was fully filled,was maintained to be about 13 MPa. That is, in this embodiment, thecarbon dioxide contained in the container body 1 was in thesupercritical state (supercritical carbon dioxide) not in the gas-liquidintermixed state.

In this embodiment, when the supercritical carbon dioxide was introducedinto the injection molding machine 100, the pressure of thesupercritical carbon dioxide was reduced so that the indication of thepressure gauge 23 was 6 MPa by using the pressure-reducing valve 60. Thepiping passage, which ranges from the pressure-reducing valve 60 to thesecond air operate valve 62, was cooled and temperature-regulated byusing an unillustrated temperature-regulating flow passage so that thetemperature of the piping passage was 20° C.

The supercritical carbon dioxide, in which the metal complex wasdissolved, was introduced into the plasticizing cylinder 40 to performthe injection molding in accordance with the same method as that of thefirst embodiment except for the step described above. As a result, amolded article, in which the metallic fine particles were impregnatedinto the surface thereof, was stably obtained in the same manner as inthe first embodiment.

Further, in this embodiment, a plating film was formed by performing theelectroless plating and the electroplating on the surface of themanufactured molded article in the same manner as in the firstembodiment. As a result, the satisfactory plating film was successfullyformed on the surface of the molded article in the same manner as in thefirst embodiment.

Fourth Embodiment

In a fourth embodiment, an explanation will be made about a method formolding the resin by using an extrusion molding machine. Those usable asthe extrusion molding method in the present invention also include theblow molding, the inflation molding or the like. All of the conventionalmethods, which include, for example, the single screw extrusion and thetwin screw extrusion, can be adopted for the mechanism of the extruderas well. The conventional manufacturing process can be also used in thepost-processes to be performed after the extrusion molding step as well.It is possible to adopt the multilayer formation and the drawing orstretching step.

In this embodiment, the following single screw extrusion molding machinewas used. That is, the extrusion of the resin was performed while thethickness of the melted resin was thinned and the area thereof wasexpanded in a fan-like form by using a die. After that, the sheet waswound by using a winding mechanism. The type of the resin usable in thisembodiment is arbitrary. In this embodiment, polycarbonate was used inthe same manner as in the first embodiment.

In this embodiment, the same metal complex (hexafluoroacetylacetonatopalladium (II)) as the metal complex used in the first embodiment wasused as the functional material. Various materials as explained in thefirst embodiment can be used as the functional material. The functionalmaterial can be appropriately selected depending on the way of use.

[Molding Apparatus]

FIG. 4 shows a schematic arrangement of a molding apparatus used in thisembodiment. As shown in FIG. 4, the molding apparatus used in thisembodiment principally includes an extrusion molding machine 200 and acarbon dioxide supply unit 201.

As shown in FIG. 4, the extrusion molding machine 200 principallyincludes a plasticizing melting cylinder 42, a hopper 30 which suppliespellets 15 of the resin into the plasticizing melting cylinder 42, amotor 50 which rotates a single screw 43 in the plasticizing meltingcylinder 42, a die 31 which performs the extrusion while thinning thethickness of the melted resin and expanding the melted resin in afan-like form, and a winding mechanism section 202. The extrusionmolding machine 200 of this embodiment is provided with introducingports for carbon dioxide at two positions. The first introducing port isa first introducing port 48 in FIG. 4 which is communicated with aportion disposed in the vicinity of a vent-mechanism section 44 of thesingle screw 43 at which the melted resin is subjected to the reductionof pressure. The second introducing port is a second introducing port 49in FIG. 4 which is communicated with a pressure-reducing section 47provided between the die 31 and the single screw 43. As shown in FIG. 4,the cross-sectional area is widened at the pressure-reducing section 47.Therefore, the pressure of the melted resin extruded from the singlescrew 43 is reduced at the pressure-reducing section 47. The resintemperature at the pressure-reducing section 47 was adjusted so that thetemperature is lower than the temperatures of those other than thepressure-reducing section by using an unillustrated band heater.

As shown in FIG. 4, the carbon dioxide supply unit 201 principallyincludes three storage containers 10, a filter 34, a pressure-reducingvalve 60, a flow rate-adjusting unit 9, two valves 13, 14, two pressuregauges 23, 25, and a piping 7 which connects the constitutive componentsas described above. As shown in FIG. 4, the output side (secondary side)of the valve 13 is connected to the first introducing port 48 of theextrusion molding machine 200 via the piping 7, which is communicatedwith the vent-mechanism section 44 in the plasticizing melting cylinder42. On the other hand, the output side of the valve 14 is connected tothe second introducing port 49 of the extrusion molding machine 200 viathe piping 7, which is communicated with the pressure-reducing section47 in the plasticizing melding cylinder 42. The storage container 10,which stores the carbon dioxide dissolved with the functional materialused in this embodiment, is constructed in the same manner as in thefirst embodiment.

[Method for Molding Resin]

Next, an explanation will be made with reference to FIG. 4 about amethod for molding the resin in this embodiment.

The liquid carbon dioxide, in which the metal complex was dissolved, wasintroduced into the extrusion molding machine 200 as follows. At first,the carbon dioxide was allowed to outflow from the storage container 10so that the indication of the pressure gauge 25 shown in FIG. 4 waswithin a range of 5.5 to 6 MPa. The pressure was adjusted to 5.5 MPa byusing the pressure-reducing valve 60. Subsequently, the liquid carbondioxide was allowed to flow while providing a constant flow rate of theliquid carbon dioxide by using the flow rate-adjusting unit 9. Thepiping 7 between the storage container and the valves 13′, 14 was filledwith the liquid carbon dioxide in which the metal complex was dissolved.

Subsequently, the liquid carbon dioxide, in which the metal complex wasdissolved, was introduced into the plasticizing cylinder 42 as follows.In this embodiment, the liquid carbon dioxide, in which the metalcomplex was dissolved, was introduced via the first introducing port 48communicated with the vent-mechanism section 44 in the plasticizingcylinder 42. At first, the pellets 15 of the resin were introduced fromthe hopper 30 into the heated plasticizing cylinder 42, and the pellets15 were melted by the rotation of the single screw 43 and the motor 50in the heated plasticizing cylinder 42. Subsequently, the valve 13 wasopened to continuously introduce the liquid carbon dioxide dissolvedwith the metal complex into the melted resin while confirming the factthat the internal pressure of the melted resin was reduced to be lowerthan the pressure of 5.5 MPa of the liquid carbon dioxide by using aninternal pressure monitor 45 for the melted resin provided at the lowerportion of the vent-mechanism section 44 at which the melted resin issubjected to the pressure reduction. Accordingly, the carbon dioxide andthe metal complex were impregnated into the melted resin. The meltedresin, in which the carbon dioxide and the metal complex wereimpregnated, is agitated again by the screw 43 at the downstream fromthe vent-mechanism section 44. Accordingly, the metal complex can bediffused uniformly to the entire resin. In this embodiment, the amountof permeation into the melted resin was adjusted by throttling the feedamounts of the liquid carbon dioxide and the metal complex from thecarbon dioxide supply unit 201 (specifically by controlling the flowrate by using the flow rate-adjusting unit).

Subsequently, the melted resin, into which the metal complex wasuniformly diffused, was fed to the die 31. The resin was extruded fromthe die 31 to the winding mechanism 202 while thinning the thickness ofthe melted resin and expanding the melted resin in a fan-like form bythe die 31. A sheet-shaped molded article 70, into which the metalcomplex was uniformly diffused, was manufactured by using the windingmechanism 202. In this embodiment, the polycarbonate molded article, inwhich the metal complex was decomposed in the molded article and thepalladium element was uniformly dispersed, was obtained in accordancewith the molding method as described above. The thermal conductively ofthe molded article of this embodiment was investigated. As a result, itwas acknowledged that the thermal conductivity was improved. Therefore,when the molding method of this embodiment is used, it is possible toproduce, at the lower cost, the molded article to be used, for example,for a heat sink material.

Fifth Embodiment

In a fifth embodiment, the liquid carbon dioxide, in which the metalcomplex was dissolved, was introduced via the second introducing port 49of the extrusion molding machine 200 used in the fourth embodiment.Except for the above, the molding process is the same as that in thefourth embodiment. The metal complex used in this embodiment was alsothe same as that used in the fourth embodiment.

As shown in FIG. 4, the second introducing port 49 of the extrusionmolding machine 200 is communicated with the pressure-reducing section47. The cross section of the flow passage for the melted resin isincreased at the pressure-reducing section 47. Therefore, the meltedresin, which is extruded from the plasticizing cylinder 42, is subjectedto the pressure reduction at the pressure-reducing section 47. Thetemperature is controlled at the pressure-reducing section 47 by usingthe band heater so that the temperature of the melted resin is lowered.In this embodiment, the valve 14 was opened to continuously introducethe liquid carbon dioxide dissolved with the metal complex into themelted resin while confirming the fact that the internal pressure of themelted resin was lower than the pressure of 5.5 MPa of the liquid carbondioxide by using the internal pressure monitor 45 for the resin providedat the pressure-reducing section 47.

However, in this embodiment, the agitation is not performed with thescrew for the resin and the carbon dioxide; The carbon dioxide and themetal complex, which are introduced in one direction, are diffused inthe lateral direction as the stretching or drawing direction of theresin at the die in the plasticizing cylinder. Therefore, an extrusionsheet 70, in which the metal complex has been impregnated into thesurface on one side, is molded. In this embodiment, the sheet-shapedpolycarbonate molded article 70, in which the metal complex wasdecomposed and the palladium metal element was dispersed in the vicinityof the surface on one side, was obtained in accordance with the methodas described above. The metal complex was dispersed in the vicinity ofthe surface without being reduced at a part of the surface of the moldedarticle 70.

Subsequently, the molded article manufactured in this embodiment wassubjected to the alkali washing and the annealing, and then the moldedarticle was immersed in an Ni-P electroless plating solution (Nicoron DKproduced by Okuno Chemical Industries Co., Ltd.) to form a nickelplating film having a thickness of 1 μm. As a result, the nickel film(hereinafter referred to as “first plating film” as well), which had noblister, was successfully formed over the entire surface of the moldedarticle. After that, a nickel film having a film thickness of 20 μm wasformed on the first plating film by means of the electroplating methodby using, as the electrode, the first plating film formed by theelectroless plating method. The plating film (nickel film) was formed onthe surface of the molded article manufactured in this embodiment inaccordance with the method described above. The cross-hatch peel testwas performed for the formed plating film. As a result, any exfoliationof the plating film was not observed. It was revealed that thesatisfactory plating film was formed.

According to the storage container of the present invention, the carbondioxide, in which the functional material has been dissolved, can besupplied by using the inexpensive apparatus without using any specialhigh pressure apparatus. Therefore, the storage container of the presentinvention is preferably usable as the supply source for the carbondioxide and the functional material capable of being used when the fiberor the molded article is modified and processed by using the carbondioxide in which the functional material has been dissolved.

In the molding method of the present invention, the functional materialcan be impregnated into the resin by using the liquid carbon dioxidehaving the low temperature and the low pressure. Therefore, the moldedarticle, in which the surface or the interior has been modified with thefunctional material, can be produced easily and inexpensively withoutusing any special high pressure apparatus for allowing the carbondioxide to be in the high pressure state or the supercritical state. Inthe molding method of the present invention, it is possible tosimultaneously perform the molding process and the surface-modifyingmethod for the resin by using the liquid carbon dioxide as the solvent.Therefore, the molding method of the present invention is preferred asthe method for producing the molded article modified with the functionalmaterial.

In the method for forming the plating film of the present invention, itis possible to simultaneously perform the molding process and thepretreatment process for the clean electroless plating. Therefore, themethod is more preferred as the method for forming the plating film. Inthe method for forming the plating film of the present invention, thesatisfactory plating film can be formed even on the polymer basematerial (resin material) for which the surface has been hardlyroughened by the etching in the case of the conventional plating methodand it has been difficult to form any electroless plating film havingthe highly tight contact or adhesion. Therefore, the method for formingthe plating film of the present invention is the method for forming theplating film which is applicable to all of the fields.

1. A storage container comprising: carbon dioxide which contains afunctional material; and a container body in which the carbon dioxidehas been hermetically contained.
 2. The storage container according toclaim 1, wherein the functional material is metallic fine particles. 3.The storage container according to claim 1, wherein the functionalmaterial is one of a hydrophilic material and a hydrophobic material. 4.The storage container according to claim 1, wherein the functionalmaterial is inorganic fine particles.
 5. The storage container accordingto claim 1, wherein the functional material is a surfactant.
 6. Thestorage container according to claim 1, wherein the carbon dioxideincludes liquid carbon dioxide having a pressure in a range of 3 MPa to7.38 MPa, and the storage container is provided with a siphon tubethrough which the liquid carbon dioxide in the container body is takenout.
 7. The storage container according to claim 6, further comprising astirring apparatus.
 8. The storage container according to claim 7,wherein the stirring apparatus includes a stirring bar which is providedin the container body, and a magnetic stirrer which drives the stirringbar.
 9. The storage container according to claim 8, wherein thecontainer body is formed of a nonmagnetic material.
 10. The storagecontainer according to claim 9, wherein the nonmagnetic material isformed of one material selected from the group consisting of aluminum,stainless steel, inconel, hastelloy, and titanium.
 11. The storagecontainer according to claim 1, wherein the carbon dioxide has apressure in a range of 3 MPa to 15 MPa.
 12. A method for molding aresin, comprising: preparing liquid carbon dioxide containing afunctional material; and impregnating the functional material into theresin by bringing the liquid carbon dioxide into contact with the resinhaving a temperature higher than that of the liquid carbon dioxide. 13.The method for molding the resin according to claim 12, wherein a stateof the resin is controlled so that the liquid carbon dioxide is changedinto one of carbon dioxide in a supercritical state and high pressurecarbon dioxide gas when the liquid carbon dioxide is brought intocontact with the resin.
 14. The method for molding the resin accordingto claim 12, which is a method for molding a thermoplastic resin usingan injection molding machine provided with a plasticizing cylinder forinjecting a melted resin into a mold, the method for molding thethermoplastic resin comprising: introducing the liquid carbon dioxidecontaining the functional material into a flow front portion of theplasticizing cylinder to bring the liquid carbon dioxide into contactwith the melted resin in the plasticizing cylinder so that thefunctional material is impregnated into the melted resin; and injectingthe melted resin in the plasticizing cylinder into the mold to fill themold therewith.
 15. The method for molding the resin according to claim12, which is a method for molding a thermoplastic resin using anextrusion molding machine, the method for molding the thermoplasticresin comprising: bringing the liquid carbon dioxide containing thefunctional material into contact with the thermoplastic resin which isin a melted state or a softened state in the extrusion molding machineto impregnate the functional material into the thermoplastic resin; andperforming extrusion molding for the thermoplastic resin into which thefunctional material has been impregnated.
 16. The method for molding theresin according to claim 12, wherein the functional material is metallicfine particles.
 17. The method for molding the resin according to claim12, wherein the functional material is one of a hydrophilic material anda hydrophobic material.
 18. The method for molding the resin accordingto claim 12, wherein the functional material is inorganic fineparticles.
 19. The method for molding the resin according to claim 12,wherein the functional material is a surfactant.
 20. The method formolding the resin according to claim 12, wherein the preparation of theliquid carbon dioxide containing the functional material includespreparing a storage container which is filled with the liquid carbondioxide containing the functional material.
 21. A method for forming aplating film, comprising: molding a molded article including metallicfine particles impregnated into a surface of the molded article by usingthe method for forming the resin as defined in claim 16; and forming theplating film by an electroless plating method on the surface of themolded article into which the metallic fine particles are has beenimpregnated.